1. Field of the Invention
The present invention relates to processing and observation of a sample using a focused ion beam apparatus.
2. Background Art
As a technique for cross-section processing and observation of a sample, such as a semiconductor, a focused ion beam has been used extensively. As an application of this technique, a 3D image of a sample interior is constructed by repetitively performing cross-section processing and observation in a specific region. Initially, a step of forming a cross section in a sample by etching processing using a focused ion beam and a step of obtaining an observation image of the cross section are performed repetitively. This operation is referred to as the cut-and-see operation. Subsequently, a plurality of obtained cross-section observation images are combined. A 3D image can be thus constructed. It is also possible to stop processing when a cross section of a desired observation subject is formed by the cut-and-see operation. A method of determining a processing end point through processing and observation of a sample defect using an FIB (Focused Ion Beam)-SEM (Scanning Electron Microscope) apparatus is disclosed, for example, in JP-A-11-273613.
In order to conduct a comparative examination and perform 3D reconstruction processing using observation images obtained by the cut-and-see operation, it is preferable that display regions in a plurality of observation images are aligned. In a case where an FIB-SEM apparatus is used, there is no need to move a stage during the cut-and-see operation. It is therefore easy to obtain continuous cross-section images in the same display range.
However, because the FIB-SEM apparatus is an expensive apparatus having a complex configuration, there has been a need to enable the cut-and-see operation by a focused ion beam apparatus that is not equipped with a SEM apparatus. On the other hand, in order to enable the cut-and-see operation by a focused ion beam apparatus that is not equipped with a SEM apparatus, there are problems as follows.
When a cross section is formed, processing is performed by irradiating a focused ion beam to a sample in a direction perpendicular to the sample. By contrast, when the cross section is observed, observation is performed by tilting the sample so that a focused ion beam is irradiated to the cross section. In other words, because the sample is tilted between processing and observation, it is necessary to tilt and move a sample stage. As an observation subject becomes finer in recent years, there has been a need for high-resolution cross-section observation. In the cut-and-see operation for high-resolution cross-section observation, displacement of the display regions among a plurality of cross sections caused when the sample stage is titled and moved is by no means negligible.
In a case where such displacement of the display regions occurs, positioning of the display region is performed in the related art by deflecting a beam to move a beam irradiation position or fine-tuning the position of the sample stage while cross-section observation is performed. The display region is positioned by viewing an observation image being positioned while a charged-particle beam is irradiated to the sample. Hence, a charged-particle beam is kept irradiated to the sample during the positioning.
However, when a charged-particle beam is kept irradiated to the sample, damage is given to the sample. More concretely, contamination adheres to the sample by an interaction of a residual gas inside a vacuum sample chamber and a charged-particle beam, a microstructure in the sample is lost by etching, and the shape of the sample is changed through an irradiation of a charged-particle beam.